What? I literally can see them collecting alder pollen in huge quantities, carrying it on their hind legs like cavalry pants and forming into highly nutritional tubes, it's possible to trace them from tree to hive - well, it's not that there is any other pollen source here now anyway. And when I collect honey, quite some amount of this stuff falls down into the tank, not mentioning cross contamination in "pollen is processed at the same facility" honey manufacturing business bees are running. At least that part of the story is certainly true, that gives some basis to disregarding the conclusions of the meta-research you found.